title: Induction of protein kinase PKR-dependent activation of interferon regulatory factor 3 by vaccinia virus occurs through adapter IPS-1 signaling.
abstract: Interferon regulatory factor 3 (IRF-3) undergoes phosphorylation-induced activation in virus-infected cells and plays an important role in the antiviral innate immune response. The E3L protein encoded by vaccinia virus is known to impair phosphorylation and activation of IRF-3. Kinases in addition to I kappaB kinase-related kinases are implicated in the IRF-3-dependent antiviral response. To test in human cells the role of the protein kinase regulated by RNA (PKR) in IRF-3 activation, HeLa cells made stably deficient in PKR using an RNA interference strategy were compared with PKR-sufficient cells. Rapid phosphorylation and nuclear accumulation of IRF-3 were detected in PKR-sufficient cells following infection with E3L deletion mutant (DeltaE3L) virus. By contrast, the full IRF-3 activation response was largely abolished in PKR-deficient cells. The DeltaE3L virus-induced IRF-3 activation seen in PKR-sufficient cells was diminished by treatment with cytosine beta-D-arabinofuranoside. Furthermore, the vaccinia mutant ts23, which displays increased viral double-stranded RNA production at 39 degrees C, induced PKR-dependent IRF-3 phosphorylation at 39 degrees C but not at 31 degrees C. Both IRF-3 phosphorylation and cell apoptosis induced by infection with DeltaE3L virus were dependent upon RIG-I-like receptor signal transduction components, including the adapter IPS-1. These data suggest that PKR facilitates the host innate immune response and apoptosis in virus-infected cells by mediating IRF-3 activation through the mitochondrial IPS-1 signal transduction pathway.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhang
authors.forename: Charles E
authors.initials: CE
authors.lastname: Samuel
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D006224:Cricetinae; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D010766:Phosphorylation; D012330:RNA, Double-Stranded / Q000737:chemistry; D015398:Signal Transduction; D014616:Vaccinia virus / Q000378:metabolism*; D019892:eIF-2 Kinase / Q000378:metabolism / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D050838:Interferon Regulatory Factor-3; C505371:MAVS protein, human; D012330:RNA, Double-Stranded; D019892:eIF-2 Kinase; D051550:I-kappa B Kinase